The present invention relates to a printing apparatus which prints patterns such as wood grain patterns and other patterns onto molded synthetic resin products such as a cabinet of a television set, a casing of a vacuum cleaner or metallic products such as aluminum sashes, etc.
Conventionally, an apparatus which prints a wood grain pattern onto a surface of a plain product by an impression plate of wood grain pattern made from a phototype has been known as a wood grain pattern printing apparatus to print on various types of products. This apparatus permits printing only on flat surfaces and cannot therefore print on curved, protruding, concave or recessed surfaces.
In addition to the above, an apparatus which transfers a wood grain pattern which is provided on a plate cylinder by means of a phototype onto a soft polyurethane roll and prints said wood grain pattern from said polyurethane cylinder onto the surface of a product is also known to be useful for the same purpose. This apparatus permits printing on curved surfaces with a large curvature but has difficulties in printing on greatly uneven surfaces or surfaces having recessed parts with small diameters.
On the other hand, an apparatus which transfers an irregular stripe pattern, prepared by dropping a printing ink on a water surface, onto a product surface by submerging the product into the water has also been known. This apparatus is disadvantageous in that it takes a long time to form a pretty stripe pattern on the water surface, it is impossible to make the same stripe pattern each time, resulting in different patterns being printed on different products and a stripe pattern transferred onto a product surface greatly differs from an actual wood grain pattern.
Furthermore, a method of molding products by mixing a plurality of types of synthetic resins of different colors and brightness has been developed as a method to form wood grain patterns. This method is also disadvantageous in that the pattern will differ with different products, a desired pattern will not be obtained and this method cannot be applied to those products other than plastic objects such as synthetic resins.
The present invention is intended to resolve the problems described above and to provide a printing apparatus capable of printing on the surfaces of objects with curved parts, projections, concavities and convexities.
The present invention provides a printing apparatus which is capable of printing the same pattern on all products.
Moreover, the present invention provides a printing apparatus which is capable of printing wood grain patterns resembling actual wood grains in a relatively short period of time.
By the printing apparatus according to the present invention, it is possible to print in colors on objects with uneven surfaces.